Dept. of Respiratory Medicine, Tohoku Univ. Graduate School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai 980-8574, JAPAN.
Am J Physiol Lung Cell Mol Physiol. 2013 Dec;305(11):L819-30. doi: 10.1152/ajplung.00053.2013. Epub 2013 Oct 4.
Airway serous secretion is essential for the maintenance of mucociliary transport in airway mucosa, which is responsible for the upregulation of mucosal immunity. Although there are many articles concerning the importance of Toll-like receptors (TLRs) in airway immune systems, the direct relationship between TLRs and airway serous secretion has not been well investigated. Here, we focused on whether TLR5 ligand flagellin, which is one of the components of Pseudomonas aeruginosa, is involved in the upregulation of airway serous secretion. Freshly isolated swine tracheal submucosal gland cells were prepared, and the standard patch-clamp technique was applied for measurements of the whole cell ionic responses of these cells. Flagellin showed potentiating effects on these oscillatory currents induced by physiologically relevant low doses of acetylcholine (ACh) in a dose-dependent manner. These potentiating effects were TLR5 dependent but TLR4 independent. Both nitric oxide (NO) synthase inhibitors and cGMP-dependent protein kinase (cGK) inhibitors abolished these flagellin-induced potentiating effects. Furthermore, TLR5 was abundantly expressed on tracheal submucosal glands. Flagellin/TLR5 signaling further accelerated the intracellular NO synthesis induced by ACh. These findings suggest that TLR5 takes part in the airway mucosal defense systems as a unique endogenous potentiator of airway serous secretions and that NO/cGMP/cGK signaling is involved in this rapid potentiation by TLR5 signaling.
气道浆液分泌对于维持气道黏膜中的黏液纤毛转运至关重要，它负责黏膜免疫的上调。尽管有许多关于 Toll 样受体（TLRs）在气道免疫系统中的重要性的文章，但 TLRs 与气道浆液分泌之间的直接关系尚未得到充分研究。在这里，我们专注于铜绿假单胞菌的一种成分鞭毛蛋白（TLR5 配体）是否参与气道浆液分泌的上调。我们制备了新鲜分离的猪气管黏膜下腺细胞，并应用标准膜片钳技术测量这些细胞对生理相关低剂量乙酰胆碱（ACh）诱导的全细胞离子反应。鞭毛蛋白以剂量依赖的方式增强了这些由生理相关低剂量 ACh 诱导的振荡电流。这些增强作用依赖于 TLR5，但不依赖于 TLR4。一氧化氮（NO）合酶抑制剂和环鸟苷酸（cGMP）依赖性蛋白激酶（cGK）抑制剂均可消除鞭毛蛋白诱导的这些增强作用。此外，TLR5 在气管黏膜下腺中大量表达。鞭毛蛋白/TLR5 信号进一步加速了 ACh 诱导的细胞内 NO 合成。这些发现表明，TLR5 作为气道浆液分泌的独特内源性增强剂参与气道黏膜防御系统，并且 NO/cGMP/cGK 信号参与 TLR5 信号的这种快速增强。
